Modification of chromatin organisation at low water potential in cultured cells of Solanum tuberosum: Possible involvement of dehydrins

ABSTRACT

To understand the mechanisms which enable the nucleus to function under low water potential, the morphology and biochemistry of potato cell nuclei were studied. Conformational modifications were observed in the chromatin of nuclei of cells growing under low water potential. These modifications include a higher number of heterochromatic centres, enlargement of the nuclear diameter, and a different accessibility of DNA to the action of restriction enzymes. Biochemical analyses showed that these chromatin modifications may coincide with quantitative and qualitative variations of several nuclear proteins, some of which may belong to the dehydrin family. We especially focussed our attention on a 45-kDa protein that is heat-stable and is recognised by an antibody raised against the conserved domain of dehydrins. The survival of potato cells in an environment where water availability is low may depend on several simultaneous events regarding the nucleus. The accumulation in the nucleus of specific proteins such as dehydrins could be required to stabilise the chromatin by means of their molecule-salvation action. Further studies are in progress to check whether or not variations in chromatin organisation may be one of the numerous traits that a cell must acquire to become water-stress resistant.     

Effect of water stress on root meristems in woody and herbaceous plants during the first stage of development

We investigated the effect of water stress on the root system architecture of pine saplings and pea seedlings during the first stage of development. Attention was focused on meristematic tissue situated at the root tip because of the leading role played by the tissue in the planning of root system architecture. The data showed that both species are extremely sensitive and that plants arrest their growth immediately during water stress treatment. When stress treatment was not intense, both species recovered growth but presented modifications in the root system architecture. In pine saplings, the modification in root system architecture was the consequence of fine root meristems not recovering from water stress. The saplings survived by producing new lateral meristems from the cortical tannin zone above the fine root tip. In the case of pea seedlings, the meristematic tissues in the primary root arrested proliferation during water stress although they recovered when the event occurred during the first hours of germination. The response was different when water stress was enforced on older seedlings. In this case, root meristems never completely recovered their proliferation despite the increase in proline content observed in the cells. The modification of root system architecture in pea seedlings depended on the arrest of primary root elongation and the formation of new root laterals. As regards the primary roots, water stress treatment induced along the axis the formation of irregular ‘swellings’ in the cortical zone above the meristematic zone. Anatomical investigations suggested that such swellings may have derived from the changes in elongation direction of derivatives. The formation of new laterals was observed in hydroponic cultures when water stress treatment was enforced slowly and prolonged for a long time. The production of new lateral meristems may have been a similar response of woody and herbaceous plants to water stress conditions. It is not known whether these new meristems present characteristics of resistance to water stress. This revised version was published online in June 2006 with corrections to the Cover Date.     

Survival of yeasts inoculated in flavoured extra virgin olive oil

The survival of four strains of yeast belonging to the speciesSaccharomyces cerevisiae, Candida wickerhamii, Candida boidinii andWilliopsis californica was studied in extra virgin olive oil flavoured with garlic, lemon, oregano and red chilli pepper. The ingredients used in the doses of 1%, 5% and 10% profoundly modified the habitat of the extra virgin olive oil, reducing drastically, in 90 days of storage, the survival of the yeasts by 20–50%, in the following decreasing order: lemon, garlic, oregano and red chilli pepper. Among the yeasts studied,W. californica strain 1639 was found to be one of the most sensitive, whileS. cerevisiae strain 1525 was one of the most tolerant regarding the ingredients present in the flavoured olive oil. The observations carried out with a scanning electron microscope (SEM) highlighted the presence of frequent lesions on the cellular wall ofC. wickerhamii 1532,C. boidinii 1638 andS. cerevisiae 1525 and only in a few rare cases inW. californica 1639. Nevertheless, since the survival ofW. californica 1639 in the flavoured olive oil was compromised to a greater extent in respect to the other species, it is plausible to deduct that the damage to the cellular wall represents only one of the causes responsible for the death of the yeasts in the flavoured olive oil.     

Controlling grape must fermentation in early winemaking phases: the role of electrochemical treatment

AIMS: To contribute to an understanding of the phenomena related to the effect of low electric current (LEC) in grape must fermentation during laboratory and pilot plant scale winemaking, with selected co-culture yeasts (Saccharomyces cerevisiae strain 404 and Hanseniaspora guilliermodii strain 465). METHODS AND RESULTS: LEC (10, 30, 50 and 100 mA) was applied to fresh grape must as an alternative method to the usual addition of SO2. Parameters such as polarity, treatment duration (24-96 h) and type of inoculum yeast were varied one at a time. LEC decreased the survival time and increased the death rate of H. guilliermondii strain 465 in co-cultures, whereas it did not affect the growth and survival of S. cerevisiae strain 40. A final comparison was made of the main physico-chemical parameters on wine obtained after the different tests. CONCLUSIONS: The results have demonstrated that the low voltage treatment using a pair of graphite electrodes had a positive effect on grape juice fermentation (yeast microflora) during the early stages of winemaking, even with the potential of being an alternative method to the usual addition of SO2. SIGNIFICANCE AND IMPACT OF THE STUDY: These results could be of significant importance in developing new winemaking technologies for an innovative yeast fermentation control process for 'biological wine'.     

Role of micromorphological leaf traits and molecular data in taxonomy of three sympatric white oak species and their hybrids (Quercus L.)

Hybridisation and introgression occur with high frequency in the genus Quercus and interspecific hybrid individuals show patterns of morphological traits that might be influenced in different ways. Micromorphological leaf traits appear to be positive and stable in Quercus species, and by combining genetic and micromorphological analyses, it is possible to compare the patterns of variation in micromorphological leaf traits of pure and hybrid individuals. Trichomes and stomatal traits were examined using scanning electron microscopy at 150–2000 × magnification in sympatric oak species collected in a natural deciduous wood. Q. frainetto, Q. petraea and Q. pubescens appear to have a relatively predictable complement of trichome types. Both the pattern and quantitative values of each micromorphological trait examined (stomata and trichomes) have an important role in identifying hybrids and pure species; putative hybrids show a pattern of trichomes that is a combination of the parental types. These results, combined with the fact that micromorphological traits generally exhibit higher consistency, indicate that this source of information can be an excellent clue to hybridisation and introgression and useful in taxonomical, systematic and evolutionary studies on the European white oaks.     

Comparative leaf surface morphology and molecular data of five oaks of the subgenus Quercus Oerst (Fagaceae)

Abstract

Comparisons between different data sets are important in taxonomic studies, particularly for complex taxa such as the genus Quercus. However, there is scarce literature on comparative morphological and molecular analyses in oaks. Here we describe an experimental approach based on the correlation between micromorphological features and molecular data in order to characterize and discriminate among five closely related species: Q. robur, Q. petraea, Q. frainetto, Q. pubescens and Q. virgiliana.     

99mTc-human immunoglobulin (HIG) in AIDS patients: first results

Scintigraphy with 99mTc labelled human polyclonal immunoglobulin was performed in 16 patients with ascertained or suspected AIDS-related infections. 99mTc-HIG lung scanning was compared, in 11 patients, with 67Ga scintigraphy, chest X-ray and high resolution lung CT. 67Ga and 99mTc-HIG were concordantly positive in five cases of BAL-ascertained Pneumocystis carinii pneumonia (PCP), while one of them was Rx and CT negative. X-ray, 67Ga and 99mTc were concordantly negative in 5 cases. 99mTc-HIG yielded negative results in two cases of Mycobacterium infection, both of which were 67Ga and Rx positive: Mycobacterium avium in diffuse lung involvement and Mycobacterium TBC in excavated infiltrate. 99mTc-HIG was also positive in other 3 AIDS patients: 1 case of intestinal cryptosporidiosis, 1 pulmonary abscess (Staphylococcus and Candida), and 1 sacral abscess; it was negative in 1 case of Kaposi sarcoma (also 201Tl negative). In conclusion, 99mTc-HIG scintigraphy in AIDS patients is feasible, and offers some practical advantages (continuous availability, fast response time, etc.). The initial results seem similar to those of 67Ga in lung scanning (and perhaps more specific for PCP).